Method and apparatus of manufacturing grooved pipe, and structure thereof

ABSTRACT

A method of manufacturing a grooved pipe includes a pressing step and a longitudinally displacing step. The pressing step presses a grooving tool toward an outer surface of a wall of a pipe in a radially inward direction of the pipe at a location, which is separated by a predetermined distance from an end portion of the pipe. The longitudinally displacing is performed by longitudinally displacing at least one of the grooving tool and the pipe relatively in a longitudinal direction of the pipe while pressing the grooving tool toward the outer surface of the wall of the pipe to form a groove portion, which is recessed from the outer surface of the wall of the pipe. The method is suitably used for forming an inner pipe of a double-wall pipe.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Applications No. 2004-325522 filed on Nov. 9, 2004, No. 2004-325521 filed on Nov. 9, 2004, No. 2005-112825 filed on Apr. 8, 2005, No. 2005-136390 filed on May 9, 2005 and No. 2005-263967, filed on Sep. 12, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for manufacturing a grooved pipe, and relates to a structure of a grooved pipe. The structure of the grooved pipe is suitably used for a double-wall pipe.

2. Description of Related Art

Conventionally, a grooved pipe is known to serve as, for example, an inner pipe, which is included in a double-wall pipe.

Unexamined Japanese Patent Publication No. 2003-329376 discloses a conventional forming method of a grooved pipe for a double-wall pipe. The double-wall pipe includes inner and outer pipes having mutually different diameters. After the inner pipe is inserted into the outer pipe, a screw thread is formed on the inner pipe by twisting the inner pipe. The screw thread is formed to enlarge a diameter of a wall of the inner pipe. Thus, ridges of the screw thread are pressed to contact an inner peripheral surface of the outer pipe. A helical groove is formed between the ridges of the screw thread to be recessed in the wall of the inner pipe.

However, a groove forming range in a longitudinal direction of the inner pipe is not stable because the screw thread is projected as well as the groove is recessed to form a grooved inner pipe by twisting the inner pipe. Also, a product quality is not stabilized because a shape of the groove is uneven. A length of the diameter of the pipe is also uneven because the screw thread is projected radially outward of the pipe. Therefore, it is difficult for the conventional grooved pipe to meet a market demand because of at least one of above-described disadvantages.

It is also disadvantageous that a projecting part of the inner pipe is strongly pressed toward the outer pipe when the double-wall pipe is formed. A part of the projecting part of the inner pipe sometimes contacts the outer pipe in a middle of a process of twisting. Thus, the conventional method is difficult to be used for twisting a long pipe. Also, a longitudinal end of the double-wall pipe needs to be sealed by an additional member (a header) because there is a gap between the diameters of the inner pipe and outer pipe. This results in an increase of a number of components and a number of processing.

SUMMARY OF THE INVENTION

In view of the above-described problems, it is an objective of the present invention to provide a method of effectively manufacturing a grooved pipe.

It is also an objective of the present invention to provide a method for manufacturing a grooved pipe having grooves extending from a predetermined location of the pipe.

It is also an objective of the present invention to provide a method of manufacturing a grooved pipe having a uniformly formed groove.

It is also an objective of the present invention to provide an apparatus for effectively manufacturing a grooved pipe.

It is also an objective of the present invention to provide an apparatus for manufacturing a grooved pipe having grooves which extend from a predetermined location of the pipe.

It is also an objective of the present invention to provide an apparatus for manufacturing a grooved pipe having a uniformly formed groove.

It is also an objective of the present invention to provide a grooved pipe having a uniformly formed groove.

According to an aspect of the present invention, a method of manufacturing a grooved pipe includes a step of pressing a grooved tool and a step of longitudinally displacing at least one of the grooving tool and the pipe. In the step of pressing, a grooving tool is pressed toward an outer surface of a wall of a pipe in a radially inward direction of the pipe at a first location, which is separated by a first predetermined distance from a first end portion of the pipe. Furthermore, in the step of longitudinally displacing, at least one of the grooving tool and the pipe is relatively displaced in a longitudinal direction of the pipe while pressing the grooving tool toward the outer surface of the wall of the pipe to form a groove portion, which is recessed from the outer surface of the wall of the pipe. Accordingly, a groove portion having a predetermined shape can be easily uniformly formed regardless of the pipe length.

For example, the longitudinally displacing can be performed from the first location to a second location, which is separated by a second predetermined distance from a second end portion of the pipe.

The method can be provided a step of circumferentially displacing at least one of the grooving tool and the pipe relatively in a circumferential direction of the pipe while pressing the grooving tool toward the outer surface of the wall of the pipe to form the groove portion. In this case, the circumferentially displacing can be performed to form a first groove extending in the circumferential direction of the groove portion, and the longitudinally displacing can be performed to form a second groove extending in the longitudinal direction from the first groove in the groove portion. Furthermore, the circumferentially displacing can be exclusively performed by a predetermined rotation angle to form a first groove in the groove portion into an arcuate shape extending in the circumferential direction. Alternatively, the circumferentially displacing can be exclusively performed by at least one revolution to form a first groove in the groove portion into an annular shape extending in the circumferential direction.

Furthermore, only the circumferentially displacing can be performed to form a first circumferential groove of the groove portion extending circumferentially at least by a predetermined angle at the first location, both the longitudinally displacing and the circumferentially displacing can be simultaneously performed to form a helical groove of the groove portion between the first location and the second location after the first circumferential groove is formed, and only the circumferentially displacing can be performed to form a second circumferential groove of the groove portion, extending circumferentially at least by a predetermined angle at the second location, after the helical groove is formed. Alternatively, only the circumferentially displacing can be performed to form a first circumferential groove of the groove portion extending circumferentially at least by a predetermined angle at the first location, only the circumferentially displacing can be performed to form a second circumferential groove extending circumferentially at least by a predetermined angle at the second location, and both the longitudinally displacing and the circumferentially displacing can be simultaneously performed to form a helical groove of the groove portion between the first location and the second location after the first and second circumferential grooves are formed.

According to another aspect of the present invention, a method of manufacturing a grooved pipe includes a step of pressing a rolling member to an outer surface of a wall of a pipe toward radially inward, and a step of relatively displacing at least one of the rolling member and the pipe while pressing the rolling member to the outer surface of the wall. In the displacing, the rolling member rolls on the wall of the pipe and forms a groove portion on the wall while the rolling. Accordingly, the groove portion can be stably uniformly formed regardless of the pipe length.

Furthermore, the rolling member and the pipe can be relatively displaced at least in one direction of an axial direction and a circumferential direction of the pipe.

The grooved pipe can be suitably used as an inner pipe for a double-wall pipe in which a passage is formed by connecting the inner pipe and an outer pipe outside the inner pipe.

According to another aspect of the present invention, a production apparatus for forming a grooved pipe includes a supporting member which support a pipe, a grooving tool which is disposed to press an outer wall of the pipe toward radially inward of the pipe and to form a groove portion on the outer wall, a pressing tool which is disposed to press the grooving tool to the outer wall toward radially inward, and a longitudinal displacing member through which at least one of the pipe and the grooving tool is relatively displaceable in a longitudinal direction of the pipe while the grooving tool presses the outer wall of the pipe. Therefore, the grooved pipe can be readily formed using the production apparatus.

The production apparatus can be provided with a rotational displacing member through which at least one of the pipe and the grooving tool is relatively displaceable in a circumferential direction of the pipe while the grooving tool presses the outer wall of the pipe. Furthermore, the grooving tool can include a plurality of grooving tool parts which are arranged at intervals in a circumferential direction of the pipe to press to the outer wall of the pipe. For example, the grooving tool includes one of a ball and a roller, rolling on the outer wall of the pipe.

According to another aspect of the present invention, a production apparatus for forming a grooved pipe includes a rolling member which is disposed to press an outer wall of a pipe toward radially inward of the pipe, and a displacing member through which at least one of the pipe and the rolling member is relatively displaced. In the production apparatus, the rolling member rolls on the outer wall of the pipe while being pressed to the outer wall to form a groove portion on the outer wall of the pipe. Therefore, the grooved pipe having a uniform groove shape can be stably formed regardless of the grooved pipe length.

According to another aspect of the present invention, a grooved pipe includes a pipe wall extending in an axial direction, the pipe wall having a first end and a second end in the axial direction, and a groove portion recessed from an outer surface of the pipe wall radially inward. In the grooved pipe, the groove portion is provided between a first location separated from the first end by a distance and a second location separated from the second end by a distance, the groove portion includes a first groove extending in a circumferential direction of the pipe wall, and a second groove extending in the axial direction, and both the first groove and the second groove are continuously provided. The first groove can be one of an arcuate shape and an annular shape, and the second groove has a helical shape extending in the axial direction. For example, the first groove includes first and second circumferential groove parts extending in the circumferential direction at the first and second locations, and the second groove is a helical groove continuously extending from the first circumferential groove part to the second circumferential groove part. In this case, a continuously extending passage extending from the first location to the second location can be formed between the inner pipe and outer pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is a partial sectional view of a double-wall pipe;

FIG. 2 is a plan view of one end portion of an inner pipe;

FIG. 3 is a front view of a production apparatus for forming a grooved pipe;

FIG. 4 is an enlarged plan view of a processing tool and a grooving tool viewed from a direction IV in FIG. 3;

FIG. 5 is a block diagram showing a method of manufacturing a grooved pipe according to a first embodiment;

FIG. 6 is a block diagram showing a method of manufacturing the grooved pipe according to the first embodiment; and

FIG. 7 is a block diagram showing method of manufacturing a grooved pipe according to a second embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS First Embodiment

In this embodiment, a double-wall pipe 10 according to the present invention is typically used for a refrigeration cycle of a vehicle air conditioning apparatus. The double-wall pipe 10 serves as a pipe for a refrigerant. The double-wall pipe 10 also serves as an internal heat exchanger for exchanging heat between a high-temperature high-pressure refrigerant from a condenser of the refrigeration cycle and a low-temperature low-pressure refrigerant from an evaporator. The double-wall pipe 10 is constructed with an outer pipe 12 and an inner pipe 11 inserted into the outer pipe 12. The low-temperature low-pressure refrigerant flows through inside the inner pipe 11. The high-temperature high-pressure refrigerant flows through a passage between the inner pipe 11 and the outer pipe 12. The inner pipe 11 of the double-wall pipe 10 includes grooves 11 b, 11 c. The grooves 11 b, 11 c are formed to be recessed from a wall surface 11 a of the inner pipe 11. The grooves 11 b, 11 c are formed by use of a production apparatus 100 for forming a grooved pipe.

Basic structures of the double-wall pipe 10 and the production apparatus 100 for forming the grooved pipe will be described with reference to FIGS. 1 to 4. FIG. 1 is a partial sectional view of the double-wall pipe 10. FIG. 2 is a plan view of one end portion of the inner pipe 11. FIG. 3 is a front view of the production apparatus 100 for forming the grooved pipe. FIG. 4 is an enlarged plan view of a processing tool 130 and a grooving tool 140 viewed from a direction IV in FIG. 3.

A length of the double-wall pipe 10 shown in FIGS. 1, 2 is about 700 to 900 mm, for example. The double-wall pipe 10 includes the inner pipe 11 and the outer pipe 12. The outer pipe 12 is located so that the inner pipe 11 penetrates through the outer pipe 12. An inner diameter of the outer pipe 12 is, for example, constantly kept at 19.6 mm in a longitudinal direction. An outer diameter of the inner pipe 11 is, for example, kept at 19.05 mm. Thus, the inner diameter of the outer pipe 12 is slightly larger than the outer diameter of the inner pipe 11. A tubular connection member 12 b is located at each end portion of the outer pipe 12. Each tubular connection member 12 b is arranged at a predetermined distance from a corresponding open end of the outer pipe 12. Each connection member 12 b is engaged with and connected to a surface of a corresponding end portion of the inner pipe 11. A burring hole 12 a is formed in each end portion of the outer pipe 12, and is arranged at a longitudinally inner side of a corresponding connection member 12 b. Each burring hole 12 a serves as a penetrating hole, which radially penetrates through a wall of the outer pipe 12. Because the burring hole 12 a is formed, a short tubular projecting pipe, which radially extending from the burring hole 12 a of the outer pipe 12, is formed. One of the burring holes 12 a is connected with an intake pipe 13 a and the other is connected with an outlet pipe 13 b. The intake pipe 13 a and the outlet pipe 13 b include flange portions connected to each other. Both the pipes 13 a, 13 b communicate with the passage between the outer pipe 12 and the inner pipe 11.

The wall surface 11 a of the inner pipe 11 between a first location corresponding to the intake pipe 13 a and a second location corresponding to the outlet pipe 13 b includes grooves, which are radially inwardly recessed from outside. The first location is positioned at a first predetermined distance from a corresponding end of the inner pipe 11. The second location is positioned at a second predetermined distance from the other end of the inner pipe 11.

The grooves include circumferential grooves 11 b and helical grooves 11 c. The circumferential grooves 11 b include first and second circumferential grooves 11 b 1, 11 b 2, which correspond to the locations of both the pipes 13 a, 13 b. Both the first and second circumferential grooves 11 b 1, 11 b 2 are formed into annular shapes. The first and second circumferential grooves 11 b 1, 11 b 2 extend in a circumferential direction of the inner pipe 11. The first circumferential groove 11 b 1 on a side of the intake pipe 13 a and the second circumferential groove 11 b 2 on a side of the outlet pipe 13 b are generally symmetrically formed. The helical grooves 11 c longitudinally extend from one of the circumferential grooves 11 b 1, 11 b 2, and connect with the other one of the circumferential grooves 11 b 1, 11 b 2. The helical grooves 11 c are structured as a multiple-thread groove (e.g., a three-thread groove). The circumferential grooves 11 b are communicated with the helical grooves 11 c. For example, three helical grooves 11 c extend from the first circumferential groove 11 b 1. The three helical grooves 11 c are joined to the second circumferential groove 11 b 2. The circumferential grooves 11 b and the helical grooves 11 c are formed continuously by use of the production apparatus 100. The production apparatus 100 will be described later. A diameter of an imaginary circle, which is formed by summit portions located between the adjacent helical grooves 11 c, is almost the same as an outer diameter of the inner pipe 11, which is not yet processed. There may be a slight clearance between an inner peripheral surface of the outer pipe 12 and the summit portions (i.e., ridge line portions). The ridge line portions may contact the inner peripheral surface of the outer pipe 12 in a case where the double-wall pipe 10 is formed into a required pipe shape (e.g., the double-wall pipe 10 is bent).

Both the pipes 13 a, 13 b directly communicate with corresponding circumferential grooves 11 b 1, 11 b 2. Inter-pipe passages 10 a, which are passages provided between the inner pipe 11 and outer pipe 12, are formed by the circumferential grooves 11 b and the helical grooves 11 c.

The double-wall pipe 10 includes a plurality of bent portions (not shown), which are bent to prevent interferences with a vehicle engine, other devices and a vehicle body. Therefore, the double-wall pipe 10 can be easily mounted in an engine room. The high-pressure refrigerant from the condenser is circulated in the inter-pipe passage 10 a between both the pipes 13 a, 13 b. The low-pressure refrigerant from the evaporator is circulated in the inner pipe 11. Thus, heat is exchanged between the high-pressure refrigerant flowing through the inter-pipe passage 10 a and the low-pressure refrigerant flowing in the inner pipe 11.

As described above, in the double-wall pipe 10 according to the present embodiment, both the end portions of the outer pipe 12 are engaged with the inner pipe 11. Also, both the circumferential grooves 11 b 1, 11 b 2 according to the present embodiment are formed at the locations, which correspond to both the pipes 13 a, 13 b. Therefore, the high-pressure refrigerant is circulated in the inter-pipe passages 10 a (the helical grooves 11 c) through the pipes 13 a, 13 b. Also, the inter-pipe passages 10 a communicate with both the pipes 13 a, 13 b through the grooves 11 b 1, 11 b 2, even when partially expanding portions expanding outwardly are not formed in the outer pipe 12 at the first and second locations.

The production apparatus 100 for producing the inner pipe 11 having the grooves will be described. The production apparatus 100 includes structures shown in FIGS. 3 and 4. A feed unit 101, which feeds a pipe material, is provided to perform a preliminary operation of the production apparatus 100. A double-wall-pipe forming unit 102, which processes the grooved pipe into the double-wall pipe 10, is provided to perform a secondary operation of the production apparatus 100. The feed unit 101 includes an uncoiler, which expands a coiled pipe member, a forming equipment and a cutter equipment. The double-wall-pipe forming unit 102 includes a pipe joining equipment, which includes an outer pipe processing equipment, a press equipment and a welding equipment, and another forming equipment, which forms the double-wall pipe 10 by bending.

The production apparatus 100 includes pipe supporting members 120 and a processing tool 130. The pipe supporting members 120 fixedly support both ends of the inner pipe 11. The processing tool 130 is moved by a longitudinal displacing member 150 (axial displacing member) and a rotational displacing member 160. The processing tool 130 includes grooving tools 140. The pipe supporting members 120 fixedly support the inner pipe 11 in a longitudinal direction (i.e., axial direction) and in a circumferential direction. The longitudinal displacing member 150 displaces the grooving tools 140 in the longitudinal direction in relative to the inner pipe 11. The rotational displacing member 160 displaces the grooving tools 140 in the circumferential direction in relative to the inner pipe 11. The longitudinal displacing member 150 and the rotational displacing member 160 displace the grooving tools 140 at the same time. Alternatively, only one of the longitudinal displacing member 150 and the rotational displacing member 160 displaces the grooving tools 140 at a time. The production apparatus 100 firstly supports the inner pipe 11 by the pipe supporting members 120. Then, the production apparatus 100 forms the circumferential grooves 11 b and the helical grooves 11 c on the wall surface 11 a of the inner pipe 11 by use of the grooving tools 140 mounted on the processing tool 130. The processing tool 130 is moved by the longitudinal displacing member 150 and the rotational displacing member 160.

The pipe supporting members 120, the processing tool 130, the grooving tools 140, the longitudinal displacing member 150 and the rotational displacing member 160 are located on a base 110, which extends in a lateral direction in FIG. 3.

The pipe supporting members 120, which serve as supporting apparatuses, includes the first chuck 121 and the second chuck 122. Each of the first chuck 121 and the second chuck 122 is located at a longitudinal end portion of the base 110. The first chuck 121 and the second chuck 122 fasten both longitudinal end portions side of the inner pipe 11 to support the inner pipe 11.

The processing tool 130, which serves as a pressing apparatus, is slidably located between the first chuck 121 and the second chuck 122. The processing tool 130 is slidable in the longitudinal direction of the base 110. Also, the processing tool 130 is rotatable in the circumferential direction of the inner pipe 11, which is a pipe material to be processed. The processing tool 130 is slidably displaceable in the longitudinal direction of the base 110 by use of the longitudinal displacing member 150, which will be described later. The processing tool 130 is rotationally displaceable in the circumferential direction of the inner pipe 11 by use of the rotational displacing member 160. The processing tool 130 includes a plurality of blocks 131. The blocks 131 are formed into fan shapes to be arranged at an identical angle in circumferential direction. The processing tool 130 is formed by arranging the blocks 131 in the circumferential direction. In the present embodiment, the processing tool 130 includes three fan-shaped blocks 131, a number of which is identical to a number of the helical grooves 11 c. Each of the three fan-shaped blocks 131 is slidably displaceable in a radial direction of the pipe, in other words, displaceably supported in the radial direction. Each block 131 may be structured like a chuck. A penetrating hole 132, into which the inner pipe 11 is inserted, is formed in a center portion of the blocks 131 when each of the blocks 131 is located at a predetermined location in the radial direction. A diameter of the penetrating hole 132 is adjustable according to a diameter of the inner pipe 11 by adjusting the locations of the blocks 131. Each fan-shaped block 131 includes a receiving hole, which penetrates through the block 131 in the radial direction. A bolt 142 is screwed into the receiving hole of each block 131, and is radially displaceable. The bolt 142 adjusts a location of a ball 141, which will be described later, in a radial direction. In the present embodiment, both of the blocks 131 and the bolts 142 are structured to be displaceable in the radial direction. The location of the ball 141 in the radial direction is adjusted by displacing either or both of the blocks 131 and the bolts 142. The processing tool 130 can be constructed with either or both of the blocks 131 and the bolts 142. The blocks 131 are displaceably located in the radial direction in a state where the inner pipe 11 is located in the penetrating hole 132. The blocks 131 are displaced manually in the present embodiment. The processing tool 130, which includes the plural blocks 131, can be provided with an operation device for a manual operation. The blocks 131 may be radially displaced by a driving device, such as an electric motor or a hydraulic system. Also, the bolts 142 may be displaced by the driving device, such as the electric motor or the hydraulic system.

Each block 131 includes the ball 141, which serves as the grooving tool 140. The balls 141 are rolling elements. In the present embodiment, three balls 142 are mounted. Each bolt 142 is arranged in each block 131 to face toward a center of the blocks 131, and is fixedly screwed to each block 131. Each ball 141 is located at an end portion of the bolt 142. The ball 141 is positioned by use of the block 131 and the bolt 142 so that a part of the ball 141 projects to the penetrating hole 132 by a predetermined amount. The ball 141 is supported in the block 131 so that the ball 141 is rotatable in all direction. A projecting amount of the ball 141 from the penetrating hole 132 corresponds to a cutting-in amount to the inner pipe 11. The projecting amount is adjustable by use of a fixing location of the bolt 142 to the block 131.

The longitudinal displacing member 150 includes a first motor 151 used as power source, a rack 152 used as a longitudinal displacing mechanism, and a pinion gear 153. The rack 152 is located to extend longitudinally along the base 110 in such a manner that teeth of the rack 152 face upward. The pinion gear 153 is engaged with the teeth of the rack 152. Also, the pinion gear 153 is supported by the processing tool 130. The pinion gear 153 is connected with the first motor 151 to be rotated by a rotation of the first motor 151. Then, the pinion gear 153 rotates along the rack 152 so that the processing tool 130 moves along the inner pipe 11 in the longitudinal direction thereof.

The rotational displacing member 160, which serves as a rotational displacing mechanism, includes a gear 162 and a second motor 161. The second motor rotates the gear 162. The gear 162 is engaged with the processing member 130. The gear 162 is rotated by a rotation of the second motor 161 so that the processing tool 130 is rotated in the circumferential direction of the inner pipe 11. The processing tool 130 includes plural blocks 131 (e.g., three blocks 131). The blocks 131 and the balls 141 supported by the blocks 131 are rotated around an axial center, which serves as a rotation center, of the inner pipe 11.

A method of manufacturing a grooved pipe by use of the production apparatus 100 will be described. A method for forming the circumferential grooves 11 b and the helical grooves 11 c on the inner pipe 11 will be described with reference to block diagrams shown in FIGS. 5 and 6.

In a feeding step 501, a pipe material, which is a subject to be processed, is fed. Then, in a first circumferential groove forming step 502, the first circumferential groove 11 b 1 is formed. After the first circumferential groove forming step 502, a helical groove forming step 503 is serially performed to form the helical grooves 11 c. As a result, the helical grooves 11 c, which serve as longitudinal grooves, directly connectedly extend from the circumferential groove 11 b 1 in the longitudinal direction of the pipe material. Then, after the helical groove forming step 503, a second circumferential groove forming step 504 is serially performed to form the second circumferential groove 11 b 2. As a result, the second circumferential groove 11 b 2, which is a circumferential groove that directly connectedly extend from the helical grooves 11 c, is formed. Then, a grooved pipe (i.e., inner pipe 11) having the groove 11 b 1, 11 c, 11 b 2 is detached from the production apparatus, in a detaching step 505.

FIG. 6 shows the production method according to the present embodiment in details. Before performing a step in FIG. 6, each block 131 of the processing member 130 is radially outwardly displaced to open the blocks 131. As a result, the penetrating hole 132 is enlarged. The inner pipe 11 fed from the feed unit 101 is inserted into the enlarged penetrating hole 132. The inner pipe 11 is located in such a manner that both the end portions of the inner pipe 11 reach the corresponding chucks 121, 122. This step is a pipe inserting step 601. Then, in a pipe chuck step 602, both the end portions of the inner pipe 11 are supported by both the chucks 121, 122, respectively. This is an end of a preparation stage.

Then, in a displacement step 603, the first motor 151 is operated so that the processing tool 130 is moved to the first location of the inner pipe 11 by use of the longitudinal displacing member 150. At the first location, the first circumferential groove 11 b 1, which is located at one longitudinal side of the inner pipe 11, is formed. As a result of the displacement of the processing tool 130, the grooving tools 140 are positioned at the predetermined first location.

Then, in the pressing step 604, each of the blocks 131 of the processing tool 130 is radially inwardly displaced. In this step, the balls 141 mounted at the end portions of the grooving tools 140 are radially inwardly cut into a wall of the inner pipe 11. Each block 131 is radially inwardly displaced so that the ball 141 is cut into the inner pipe 11 by a predetermined amount. This step is also named as a ball clamping step of the processing tool.

Then, in a rotational and longitudinal displacing step 605, the grooving tools 140 are longitudinally and circumferentially displaced along the inner pipe 11 by use of the rotational displacing member 160 and the longitudinal displacing member 150 to form the grooves 11 b, 11 c. Firstly, a rotational displacing step is performed. In this step, only the rotational displacing member 160 is exclusively operated to rotate the grooving tools 140 at the first location. At this time, the grooving tools 140 are not displaced in the longitudinal direction. A rotational angle of the grooving tools 140 can be set equal to or more than 120°. In other words, when the plurality of balls 141 form a circumferential groove that circumferentially encircles the inner pipe 11 by rotating the grooving tools 140 by a minimum angle, the rotational angle of the grooving tools 140 may be set equal to or more than the minimum angle. In the present embodiment, for example, three balls 141 are arranged around an axis of the inner pipe 11, which is the pipe material to be processed. Thus, the first circumferential groove 11 b 1 is annularly formed. Then, the rotational displacing step and the longitudinal displacing step are simultaneously performed. In the present embodiment, the rotational displacing member 160 is driven as well as the longitudinal displacing member 150 is driven. As a result, the grooving tools 140 are rotated and also displaced along the inner pipe 11 in the longitudinal direction of the inner pipe 11. Therefore, the grooving tools 140 are displaced to draw helical traces on the surface of the inner pipe 11. Thus, the helical grooves 11 c, which connectedly extend from the first circumferential groove 11 b, is formed. In the present embodiment, three helical grooves 11 c are formed by using three grooving tools 140. This helical groove forming step is performed for the inner pipe 11 from the first location to the second location of the pipe 11. When the grooving tools 140 reach the second location, the rotational displacing step is exclusively performed again. When the grooving tools 140 reach the other longitudinal end side of the inner pipe 11 to form the second circumferential groove 11 b 2, the longitudinal displacing member 150 is stopped while the rotational displacing member 160 is operated. Then, the second circumferential groove 11 b 2 is formed. When the forming of the second annular circumferential groove 11 b 2 is ended, the rotational displacing member 160 is stopped. While the grooves 11 b 1, 11 c, 11 b 2 are formed, the balls 141 of the grooving tools 140 roll on the inner pipe 11 to move.

In a releasing step 606, which serves as a detaching step, each block 131 of the processing tool 130 is radially outwardly displaced to detach the grooving tools 140 from the inner pipe 11. Then, in a removing step 607, support of the inner pipe 11 by use of each chuck 121, 122 is released so that the inner pipe 11, which is formed into the grooved pipe, is removed from the production apparatus 100.

According to the present embodiment, the grooving tools 140 are pressed to the inner pipe 11 at a grooving start position. Then, at a grooving end position, the grooving tools 140 are detached from the inner pipe 11. As a result, a starting point and an ending point of the groove are clearly set. Furthermore, in the present embodiment, the balls 141, which serves as rolling elements, roll on the wall surface 11 a of the inner pipe 11 to cut the wall surface 11 a so that the grooves 11 b, 11 c are formed. Thus, shapes (e.g., a depth and a thickness) of the grooves are stabilized. In the process of grooving, the grooving tools 140 are displaced while they are pressed toward the inner pipe 11 by use of the longitudinal displacing member 150 and the rotational displacing member 160. Thus, a required groove is accurately formed regardless of a length of the inner pipe 11. Further, both the end portions of the inner pipe 11 are fixed while the wall surface 11 a of the inner pipe 11 is recessed to form grooves 11 b, 11 c. Thus, a change of the length of the inner pipe 11 is limited. In addition, an outer diameter of a general portion of the inner pipe 11, without being cut, remains generally identical to an original size, and remains constant.

In this embodiment, the grooving tools 140 are displaced exclusively in the circumferential direction of the inner pipe 11 to form the circumferential grooves 11 b. Also, after this, the grooving tools 140 are additionally displaced in the longitudinal direction of the inner pipe 11 while the grooving tools 140 are displaced in the circumferential direction. Thus, the helical grooves 11 c, which extend from the first circumferential groove 11 b 1, are easily formed. After the grooving tools 140 are displaced in the circumferential direction as well as the longitudinal direction of the inner pipe 11, the displacement of the grooving tools 140 in the longitudinal direction is stopped while the rotation in the circumferential direction is continued. Thus, the second circumferential groove 11 b 2, which is connected to the helical grooves 11 c, is easily formed. Furthermore, at least one of the starting point and the ending point of the process of grooving is located at the circumferential grooves 11 b. Thus, the passage between the inner pipe 11 and outer pipe 12 of the double-wall pipe 10 is certainly communicated with the grooves 11 c, 11 b when the double-wall pipe 10 is formed.

Because the processing tool 130 includes the plurality of the grooving tools 140 to simultaneously form the plural grooves 11 c, the plural grooves 11 c can be easily formed to have a predetermined pattern.

The balls 141 of the grooving tools 140 are supported so that the balls 141 roll in the processing tool 130. Thus, the grooves 11 b, 11 c are formed while the balls 141 roll on the wall surface 11 a of the inner pipe 11. Therefore, the friction while the grooves 11 b, 11 c are formed is reduced. Also, stress toward the wall surface 11 a of the inner pipe 11 is limited. Thus, the process of grooving is made easier and burrs or scorings are limited. Also, quick processing is made possible because the balls 141 roll to form the grooves 11 b, 11 c.

Second Embodiment

A second embodiment of the present invention will be described with reference to the accompanying drawings. Similar components of a production apparatus forming a grooved pipe of the present embodiment, which are similar to the components of the production apparatus of the grooved pipe of the first embodiment, will be indicated by the same numerals.

FIG. 7 is a block diagram of a production method for manufacturing the grooved pipe according to the second embodiment. In the present embodiment, the production apparatus 100 shown in FIGS. 3, 4 can be used, and a displacement of the blocks 131 in the radial direction is driven by a driving device, such as a motor.

In a feeding step 710, a pipe material to be processed for forming the inner pipe 11 is fed. In a cutting and forming step 711, a predetermined length of the pipe material is cut from a pipe coil. The cut pipe material is formed into a tubular shape to be fed. In a feeding and inserting step 712, the pipe material is inserted into the production apparatus 100, and is positioned at a predetermined location. In a chuck step 713, both the end portions of the pipe material are fixedly supported by the chucks 121, 122.

Then, a groove processing step 720 is performed. In the groove processing step 720, firstly, the first circumferential groove 11 b 1 is formed in a first circumferential groove step 723. Secondly, the second circumferential groove 11 b 2 is formed in a second circumferential groove step 727. Then, the helical grooves 11 c between the circumferential grooves 11 b 1, 11 b 2 are formed in a helical groove step 729. Thus, in the present embodiment, the helical grooves 11 c are formed to extend from the second circumferential groove 11 b 2 so that the second circumferential groove 11 b 2 is connected with the helical grooves 11 c. Also, the helical grooves 11 c are formed to join to the first circumferential groove 11 b 1, which is formed in advance. Thus, the first circumferential groove 11 b 1 is connected with the helical grooves 11 c.

In a displacing step 721, the processing tool 130 is displaced to the first location. At the first location, the grooving tools 140 are displaced at the location, where the grooving tools 140 form the first circumferential groove 11 b 1. Then, in a rotation starting step 722, the rotational displacing of the processing tool 130 is started. The rotational displacing is continued to the end of the series of the process of grooving. Then, in a ball clamping step 724, the balls 141 are pressed toward the wall surface 11 a of the inner pipe 11. In the present embodiment, the rolling balls 141 slowly cut into the wall surface 11 a of the inner pipe 11. As a result, the first circumferential groove 11 b 1 is formed. Then, in a ball retreating step 725, the balls 141 are radially outwardly moved. In a displacing step 726, the processing tool 130 is displaced to the second location. At the second location, the grooving tools 140 are displaced at the location, where the grooving tools 140 form the second circumferential groove 11 b 2. In the displacing step 726, the grooving tools 140 are displaced from the first location to the second location. However, grooves are not formed in this displacing because the balls 141 are retreated radially outwardly.

In a ball clamping step 728, the balls 141 are pressed toward the wall surface 11 a of the inner pipe 11. In the present embodiment, the rolling balls 141 slowly cut into the wall surface 11 a of the inner pipe 11. As a result, the second circumferential groove 11 b 2 is formed. Then, in a longitudinal displacing starting step 730, a longitudinal displacing step is started. The longitudinal displacing step is continued until the grooving tools 140 reach the first location from the second location. As a result, the rotational displacing step and the longitudinal displacing step are simultaneously performed to form the helical grooves 11 c on the wall surface 11 a of the inner pipe 11. The helical grooves 11 c are formed to reach the first circumferential groove 11 b 1, which is formed in advance. This means that the helical grooves 11 c are joined to the first circumferential groove 11 b 1. At this timing, a longitudinal displacing stopping step 731 is performed to stop the longitudinal displacing step. As a result, the balls 141 are positioned in the first circumferential groove 11 b 1 again. Then, in a ball retreating step 732, the balls 141 are radially outwardly moved. Then, in a rotational displacing stopping step 733, the rotational displacing step is stopped. Then, in a displacing step 734, the processing tool 130 is relocated at an initial position to end the series of the process of grooving.

In a detaching step 740, the chucks 121, 122 are released to detach the inner pipe 11, which serves as the grooved pipe. Then, the inner pipe 11 is fed to the nest operation. Then, in a double-wall pipe assembling step 750, the inner pipe 11 is inserted into and fixed to the outer pipe 12, which is formed from a pipe material. Also, in a forming step 760, the double-wall pipe 10 is formed into a predetermined shape. For example, a bending process is operated in the forming step 760.

In this production method, after the first circumferential groove 11 b 1 is formed, the helical grooves 11 c are formed to extend to the first position from the second position. Then, the helical grooves 11 c are joined to the first circumferential groove 11 b 1. As a result, both the grooves 11 b 1, 11 c communicate with each other. Therefore, undesired deformation of the wall surface 11 a of the inner pipe 11 is restricted.

Other Embodiments

Alternative structures of an above-described embodiment or additional structures to the above-described embodiment will be described.

The grooves provided on the inner pipe 11 further include other types of grooves. For example, grooves having different twist angles can be provided. Also, grooves having different pitches can be provided. Specifically, a straight groove that extends in the longitudinal direction may be formed. Also, grooves, the twist angles of which are opposite, may be formed to cross with other.

In the above-described embodiment, the outer pipe 12 is a uniform pipe without a groove and a diameter of the outer pipe 12 is constant. However, the outer pipe 12 may be grooved.

In the above-described embodiment, the grooves are continuously located between the first location and the second location. However, only a part of the whole inner pipe 11 may be grooved. A plurality of grooves, which are not directly communicated with each other, may be formed in parallel. Also, the circumferential grooves 11 b may be formed at a longitudinally center portion of the inner pipe 11 in addition to connecting portions to the passages at the two end portions. At one end of the grooved pipe, the groove may be formed to extend to an edge of the end portion of the pipe. In the above-described embodiment, a depth of the groove is constant. However, the depth of the groove may be changed according to a longitudinal location of the groove. For example, the radial location of the blocks 131, in other words, the cutting-in amount of the balls 141 into the wall surface 11 a of the inner pipe 11, may be changed during the process of grooving.

In the above-described embodiment, the inner pipe 11 is engaged with the outer pipe 12 by use of structures, such as direct soldering or welding. However, rubber O-ring may be located between the inner pipe 11 and the outer pipe 12 to seal a passage between the inner pipe 11 and the outer pipe 12. The passage between the inner pipe 11 and the outer pipe 12 may also be closed by an end cap portion, which includes a connection member connected with an end portion of the inner pipe 11 and another connection member connected with an end portion of the outer pipe 12.

In the first embodiment, after the grooving tools 140 are displaced exclusively in the circumferential direction of the inner pipe 11, the grooving tools 140 are displaced in the circumferential direction and in the longitudinal direction. Therefore, the grooving tools 140 are displaced exclusively in the circumferential direction. As a result, the circumferential grooves 11 b are formed at a starting portion and an ending portion, and the helical grooves 11 c are formed between the starting portion and the ending portion. However, various shapes of grooves may be formed by combining the displacement of the grooving tools 140 in the circumferential direction and in the longitudinal direction.

For example, an arc-shaped groove may be formed to extend in the circumferential direction by rotating the grooving tools 140 in the circumferential direction by a predetermined angle, which is equal to or less than 360°. When the grooving tools 140 are displaced exclusively in the longitudinal direction and not displaced in the circumferential direction, a straight groove is formed to extend in the longitudinal direction. Also, when the grooving tools 140 are displaced in the circumferential direction as well as the grooving tools 140 are substantially slowly displaced in the longitudinal direction, a groove, which corresponds to a wide circumferential groove, may be formed. When the grooving tools 140 are alternately rotated in one circumferential direction and the other circumferential direction as well as the grooving tools 140 are displaced in the longitudinal direction, a meandering groove may be formed.

Also, a structural member, which serves as an alternative of the ball 141, of the end portion of each grooving tool 140 may be a flat roller. A width of the flat roller corresponds to a width of the groove. Also, a surface, which contacts the inner pipe 11, of the flat roller can be set arcuate. The roller, which serves as the rolling element, may be structured to be able to change directions of rolling according to changes of a relative displacement direction during the feeding step. For example, the roller may be supported by a steering mechanism so that the roller is enabled to change directions of rolling. Also, the structural member may be a curved-surface projection member, which integrally projects from the bolt 142.

In the above-described embodiment, the processing tool 130 includes a plurality of blocks 131, which are radially displaceable. However, the blocks 131 may be integrated into one block. Then, the grooving tools 140, or the bolts 142, may be slidably radially displaceable to make the balls 141 cut into the inner pipe 11 or to detach the ball 141 from the inner pipe 11.

In the above-described embodiment, the grooving tools 140 are displaced relative to the inner pipe 11 along with the processing tool 130 to form the groove. However, the inner pipe 11 may be displaced relative to the grooving tools 140, which are fixed. Alternatively, both the inner pipe 11 and the grooving tools 140 may be relatively displaced.

In the above-described embodiment, a usage of the inner pipe 11 for the double-wall pipe 12 is typically described. However, the inner pipe 11 may be used in various applications, which use grooved pipes.

Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. 

1. A method of manufacturing a grooved pipe, comprising: pressing a grooving tool toward an outer surface of a wall of a pipe in a radially inward direction of the pipe at a first location, which is separated by a first predetermined distance from a first end portion of the pipe; longitudinally displacing at least one of the grooving tool and the pipe relatively in a longitudinal direction of the pipe while pressing the grooving tool toward the outer surface of the wall of the pipe to form a groove portion, which is recessed from the outer surface of the wall of the pipe.
 2. The method according to claim 1, wherein the longitudinally displacing is performed from the first location to a second location, which is separated by a second predetermined distance from a second end portion of the pipe, the method further comprising: detaching the grooving tool from the outer surface of the wall of the pipe in a radially outward direction of the pipe, wherein the detaching is performed after the longitudinally displacing is performed.
 3. The method according to claim 1, further comprising circumferentially displacing at least one of the grooving tool and the pipe relatively in a circumferential direction of the pipe while pressing the grooving tool toward the outer surface of the wall of the pipe to form the groove portion.
 4. The method according to claim 3, wherein: the circumferentially displacing is performed, to form a first groove extending in the circumferential direction in the groove portion; and the longitudinally displacing is performed, to form a second groove extending in the longitudinal direction from the first groove in the groove portion.
 5. The method according to claim 3, wherein the circumferentially displacing is exclusively performed by a predetermined rotation angle to form a first groove in the groove portion into an arcuate shape, the first groove extending in the circumferential direction.
 6. The method according to claim 3, wherein the circumferentially displacing is exclusively performed by at least one revolution to form a first groove in the groove portion into an annular shape, the first groove extending in the circumferential direction.
 7. The method according to claim 3, wherein the grooving tool is circumferentially displaced while the longitudinally displacing is performed in at least one of the following situations: before the circumferentially displacing is exclusively performed to form a first groove extending in the circumferential direction in the groove portion; and after the circumferentially displacing is exclusively performed to form a first groove extending in the circumferential direction in the groove portion, whereby at least a second groove extending in the longitudinal direction is formed to extend from the first groove in the groove portion.
 8. The method according to claim 3, wherein the longitudinally displacing and the circumferentially displacing are simultaneously performed to form a helical groove in the groove portion.
 9. The method according to claim 3, wherein the circumferentially displacing is exclusively performed in at least one of the following situations: before the longitudinally displacing and the circumferentially displacing are simultaneously performed; and after the longitudinally displacing and the circumferentially displacing are simultaneously performed, whereby at least a groove extending in the circumferential direction is formed.
 10. The method according to claim 1, wherein: the pressing is performed using a plurality of grooving tools; and the plurality of grooving tools is arranged in the circumferential direction of the pipe at predetermined intervals to press the pipe.
 11. The method according to claim 1, wherein the grooving tool includes a rolling element, which rolls on the wall of the pipe to form the groove portion on the wall of the pipe while relatively displacing at least one of the grooving tool and the pipe.
 12. The method according to claim 3, wherein: the groove portion is formed between the first location and a second location separated from the first location in the longitudinal direction; only the circumferentially displacing is performed to form a first circumferential groove of the groove portion, extending circumferentially at least by a predetermined angle at the first location; both the longitudinally displacing and the circumferentially displacing are simultaneously performed to form a helical groove of the groove portion between the first location and the second location, after the first circumferential groove is formed; and only the circumferentially displacing is performed to form a second circumferential groove of the groove portion, extending circumferentially at least by a predetermined angle at the second location, after the helical groove is formed.
 13. The method according to claim 3, wherein: the groove portion is formed between the first location and a second location separated from the first location in the longitudinal direction; only the circumferentially displacing is performed to form a first circumferential groove of the groove portion, extending circumferentially at least by a predetermined angle at the first location; only the circumferentially displacing is performed to form a second circumferential groove of the groove portion, extending circumferentially at least by a predetermined angle at the second location; and both the longitudinally displacing and the circumferentially displacing are simultaneously performed to form a helical groove of the groove portion between the first location and the second location, after the first and second circumferential grooves are formed.
 14. A method of manufacturing a grooved pipe, comprising: pressing a rolling member to an outer surface of a wall of a pipe toward radially inward; and relatively displacing at least one of the rolling member and the pipe while pressing the rolling member to the outer surface of the wall, wherein in the displacing, the rolling member rolls on the wall of the pipe and forms a groove portion on the wall while the rolling.
 15. The method according to claim 14, wherein, in the displacing, the rolling member and the pipe are relatively displaced at least in one direction of an axial direction and a circumferential direction of the pipe.
 16. The method according to claim 1, wherein the grooved pipe is an inner pipe for a double-wall pipe in which a passage is formed by connecting the inner pipe and an outer pipe outside the inner pipe.
 17. A production apparatus comprising: a supporting member which support a pipe; a grooving tool which is disposed to press an outer wall of the pipe toward radially inward of the pipe and to form a groove portion on the outer wall; a pressing tool which is disposed to press the grooving tool to the outer wall toward radially inward; and a longitudinal displacing member through which at least one of the pipe and the grooving tool is relatively displaceable in a longitudinal direction of the pipe while the grooving tool presses the outer wall of the pipe.
 18. The production apparatus according to claim 17, further comprising: a rotational displacing member through which at least one of the pipe and the grooving tool is relatively displaceable in a circumferential direction of the pipe while the grooving tool presses the outer wall of the pipe.
 19. The production apparatus according to claim 17, wherein the grooving tool includes a plurality of grooving tool parts which are arranged at intervals in a circumferential direction of the pipe to press to the outer wall of the pipe.
 20. The production apparatus according to claim 17, wherein the grooving tool includes one of a ball and a roller, rolling on the outer wall of the pipe.
 21. The production apparatus according to claim 17, wherein the grooving tool includes a rolling member which rolls on the outer wall of the pipe while pressing the outer wall, to form the groove portion.
 22. A production apparatus comprising: a rolling member which is disposed to press an outer wall of a pipe toward radially inward of the pipe; and a displacing member through which at least one of the pipe and the rolling member is relatively displaced, wherein the rolling member rolls on the outer wall of the pipe while being pressed to the outer wall to form a groove portion on the outer wall of the pipe.
 23. The production apparatus according to claim 22, wherein the displacing member is disposed to displace the rolling member in relative to the pipe at least in one direction of a longitudinal direction and the circumferential direction of the pipe.
 24. A grooved pipe comprising: a pipe wall extending in an axial direction, the pipe wall having a first end and a second end in the axial direction; and a groove portion recessed from an outer surface of the pipe wall radially inward, wherein: the groove portion is provided between a first location separated from the first end by a distance and a second location separated from the second end by a distance; the groove portion includes a first groove extending in a circumferential direction of the pipe wall, and a second groove extending in the axial direction; and both the first groove and the second groove are continuously provided.
 25. The grooved pipe according to claim 24, wherein the first groove has one of an arcuate shape and an annular shape.
 26. The grooved pipe according to claim 24, wherein the second groove has a helical shape extending in the axial direction.
 27. The grooved pipe according to claim 24, wherein: the first groove includes first and second circumferential groove parts extending in the circumferential direction at the first and second locations; and the second groove is a helical groove continuously extending from the first circumferential groove part to the second circumferential groove part. 